A turbomachine habitually contains at least one portion dedicated to compressing the air which it takes in. This compressed air enters a combustion chamber, where it is mixed with a fuel before the resulting mix is ignited, producing hot combustion gases. These gases are then decompressed in a high-pressure stage of the turbine, and then in at least one low-pressure stage of this same turbine.
Each stage of the turbine generally includes a series of fixed blades (or distributors), followed by at least one (turbine) rotor. This rotor contains at least two series of moving blades which are attached respectively to disks which are rotationally coupled to one another.
Each disk in fact includes a coupling portion with recesses (or cells), which each hold a blade root of a series. In addition, in a conventional rotor, most of the disks include an “upstream” arm and a “downstream” arm which is rotationally coupled to the upstream arm of the next disk by bolted joints.
Due to the increasingly constrained environment of turbines in terms of operating temperatures and rotor rotation speeds, and to the increasingly large diameters of these turbines, phenomena occur of separation of flanges, and of high stresses in the inter-disk bolted joints. These joints also involve very considerable accessibility constraints for installation equipment.
To reduce the temperature stress in order to give the portions coupling the blades (blade roots) and the disks longer lifetimes, they should be cooled by means of cooling air, which is guided to them (and in particular as far as the blade root recesses (or cells)), without being mixed in with the hot stream air which flows under the low-pressure distributors (or DBPs). Indeed, such mixing would heat the cooling air, leading to a loss of cooling function at the base of the cell.
In a conventional rotor (with inter-disk bolted joints) the cooling air is guided by a labyrinth ring which is attached via a flange to the bolted joints, and which is positioned in front of an “outer” face of the disk's upstream arm, as described in patent document FR 3019584. This flange contains holes allowing air to enter a space defined between the “inner” face of the labyrinth ring and the outer face of the disk's upstream arm.
In order to reduce the phenomena of separation of flanges and the stresses in the inter-disk bolted joints, while reducing the rotor's total mass, it has been proposed to reduce the mass, the encumbrance and possibly the number of inter-disk bolted joints. Such rotors are generally of the “spool” or “drilled” type.
In both these rotor types inclusion of the cooling air supply means intended for the blade/disk coupling portions poses problems. More specifically, a spool rotor does not enable a labyrinth ring to be included, and the addition of a labyrinth ring between the disks of a drilled rotor makes this type of rotor substantially heavier, and requires an additional flange on each inter-disk screwed joint, increasing the weight still further, and making assembly more complex.